The invention relates to a ball joint having a joint housing, a bearing shell received in the joint housing, and a ball stud having a ball head arranged for pivoting movement in the bearing shell.
Ball joints are used in various forms, for example for vehicles. For such ball joints it is known to receive a bearing shell in the joint housing, a ball head of a ball stud being arranged in an articulated manner in the bearing shell. The bearing shell is in most cases made of a plastic material which results in favorable sliding or friction coefficients between the ball head and the bearing shell and at the same time in favorable manufacturing costs. The wear occurring over the lifetime of the ball joint is compensated by an axial prestress applied to the ball head substantially in the direction of a longitudinal axis of the ball stud. A free play in the joint can be avoided by such a prestress.
The prior art shows various technologies to cause the ball head of a ball joint to be prestressed with respect to the housing.
U.S. Pat. No. 5,188,477 shows an axial ball joint open on one side in which an elastomer element is arranged between a bottom face in the interior of the housing and the bearing shell. Here, the bearing shell is received in the housing such that the elastomer element is pressurized. The elastomer element thus exerts an axial force on the bearing shell so that the ball head arranged within the bearing shell is substantially prestressed in a direction of the longitudinal axis of the ball stud.
Documents U.S. Pat. No. 3,226,142 and U.S. Pat. No. 4,225,260 each show a radial ball joint in which an elastomer ring is placed between a housing cover which closes an opening of the joint housing and an edge-side shoulder section of the bearing shell. In the assembled state of the joint, this elastomer ring tensions the bearing shell in the axial direction so that the ball head is thereby prestressed substantially in the direction of a longitudinal axis of the ball stud. As already explained, such a prestress counteracts the wear over the lifetime of the joint and prevents the occurrence of a free play or similar.
In ball joints of a different type, it is known to cause the bearing shell to be prestressed with respect to the housing cover using a metal spiral spring. This is disclosed for example in EP 348 642, U.S. Pat. No. 924,029 or DE 1 678 052. The spiral spring rests against the housing cover and presses the bearing shell or the upper shell of the bearing means against the ball head. Here, the prestress of the spiral spring defines the pressure force of the bearing shell on the ball head and simultaneously determines the operating characteristic values of the ball joint. Due to the prestress of the bearing shell, a wear within the ball joint can at the same time be compensated.
Furthermore, a ball joint 110 is known from the prior art (see FIG. 25), in which a spring system in the form of a disk spring 128 is provided between the housing cover 124 and the bearing shell 114 in the assembled state of the joint. Due to the prestress of this disk spring 128, the bearing shell 114 is pressed against the ball head 118 of the ball stud 116 such that even if a wear of the bearing shell 114 occurs, a permanent contact between the bearing shell 114 and the ball head 118 is present and no free play occurs between the ball head 118 and the bearing shell 114. The disk spring 128 is to be understood as a series connection of spring elements and ensures a predetermined desired spring characteristic. The drawback of this known joint is the comparatively high space requirement of the disk spring and the high material costs thereof.